The traditional way of dyeing yarns has been to steep hanks of the yarn in vats of dyestuff to impregnate the yarn with the dyestuff and then remove the hanks from the vat and allow them to drain and dry.
However, yarns dyed by that traditional method usually exhibit undesirable variations in colour due to differing degress of take-up of the dyestuff by the yarn in different parts of the hank. This effect is particularly marked when using modern synthetic materials of the kind mentioned above.
Thus, it has now become customary to spray or print the dyestuff on to a moving strand, a web of parallel strands or a knitted or woven sheet of the yarn (which sheet may subsequently be unravelled) to ensure an even application of the dyestuff to the yarn.
Hitherto, it has been thought necessary for such printing or spraying to be carried out utilising liquid dyestuffs at room temperature, following which, the yarn is steam or otherwise heated to set the dye. Thus, to obtain even colouration, a relatively complex two step process is currently used involving relatively complex apparatus including a steam-heating chamber, oven or the like.
An object of the present invention is to simplify the abovementioned presently used process.